Taxon Details: Megalastrum peregrinum Sundue, Rouhan & R.C.Moran
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Family:
Dryopteridaceae (Pteridophyta)
Dryopteridaceae (Pteridophyta)
Scientific Name:
Megalastrum peregrinum Sundue, Rouhan & R.C.Moran
Megalastrum peregrinum Sundue, Rouhan & R.C.Moran
Accepted Name:
This name is currently accepted.
This name is currently accepted.
Description:
by: M. Sundue, G. Rouhan and R.C. Moran
Description: Plants terrestrial; es erect, ca. 1.5 cm wide; fronds 0.35-1 m long; basal petiole scales 3.0 × 0.1-0.15 cm, linear-lanceolate, light brown, translucent, minutely denticulate, twisted, the cells elongate; laminae 30-60 cm long, 3-pinnate at base, 2-pinnate-pinnatifid medially; basal pinna 12-22 cm long, inaequilateral, short-stalked; pinnules sessile, the basal segments frequently overlapping the pinna rachis, the largest pinnule of the basal pinna 7-9 cm long; pinna rachises abaxially glandular, scaly, and densely pubescent, the glands sessile, globose, 0.1 mm long, the hairs 0.2-0.4 mm long, 3- or 4-celled, hyaline, acicular, the cross walls reddish, the scales 1.5-4.0 × 0.4-1.2 mm, ovate to lanceolate, translucent, light brown, slightly bicolorous, the center darker than the edges, entire, the cells isodiametric, adaxial pinna rachises not seen; costules abaxially glandular, scaly, and pubescent, the glands like those of the costae, the scales 1.5-2.5 × 0.5 mm, ovate to lanceolate, the apices attenuate, up to 1/3 the length of the scale, otherwise similar to those of the pinna rachises, the hairs similar to those of the abaxial costae, adaxial costules not seen; lamina tissue between the veins abaxially glandular and sparsely pubescent, the glands sessile, globose, 0.1 mm long, the hairs 0.2-0.3 mm long, 2-celled, erect, adaxially glandular and pubescent the glands sessile, globose, 0.1 mm long, the hairs 0.3-0.5 mm long, 3- or 4-celled, spreading; veins not visible on either side of the lamina, abaxially glandular, pubescent, and provided with scales along the main vein, the hairs 0.3-0.5 mm long, 3- or 4-celled, adaxially pubescent, the hairs like those between the veins; lamina margins recurved, ciliate, the hairs 0.2-0.4 mm long, 2- or 3-celled, acicular; indusia present, 0.3-0.4 mm wide, light brown, fugacious, the surface and margins with sessile glands, ca. 0.1 mm long, and sometimes with 1 or 2 setae, ca. 0.1 mm long; spores echinate (Tryon and Lugardon 1990: 460 as Ctenitis aquilina)
Distribution: Distribution and habitat.- Endemic to Gough Island in the South Atlantic Ocean, which is part of the Tristan da Cunha archipelago; among rocks, on banks, in the open, or under stands of Phylica arborea ca. 55-500 m.
Comments: Megalastrum peregrinum is distinguished from all other species in the circumaustral region by the lamina tissue between the veins adaxially pubescent and glandular. In other aspects, M. peregrinum is similar to M. spectabile of Chile and Argentina, M. aquilinum of Tristan da Cunha and Gough Islands, and M. taafense of Île Amsterdam and Île Saint-Paul. In addition to the indument of the adaxial laminae, it differs from M. spectabile in having recurved lamina margins, a fugacious indusia, and longer scales (1.5-2.5 mm long vs. 0.5-1.2 mm long) on the abaxial costules, and from M. aquilinum and. M. taafense by the adaxial indument, and having more densely ciliate lamina margins and longer scales (1.5-2.5 mm long vs. 1.0-1.5 mm long) on the abaxial costules. The South Altlantic islands of the Tristan archipelago, including Tristan da Cunha, the Nightingale group, Inaccessible, and Gough Island, are about 1750 miles west of South Africa and 2088 miles east of South America. Gough Island lies 230 miles southeast of the other islands in the Tristan da Cunha archipelago. All the islands are of recent volcanic origin, with ages of 1 million years (Tristan), 6 million years (Gough), 8 million years (Inaccessible), and 16 million years (Nightingale group) (Wace and Dickson 1965). The islands have a temperate flora that is low in diversity, but rich in ferns. About half of the vascular plant diversity is comprised of ferns and lycophytes (Christensen 1940; Tryon 1966; Wace and Holdgate 1958). The islands' flora is notable for its high endemism: at least half of its species or varieties of ferns and lycophytes are endemic (Christensen 1940; Tryon 1966). The addition of M. peregrinum brings the number of ferns and lycophyte species in the island group up to 34. Based on the young age of the Tristan da Cunha archipelago and the similarity of M. peregrinum to the South-American M. spectabile, an allopatric origin of this species through long-distance dispersal from South America is likely. A similar long-distance dispersal event has been inferred for several species in the "ciliatum group" of Elaphoglossum on Tristan da Cunha (Vasco et al. in press.). Alternatively, M. peregrinum might have evolved locally on the islands from M. aquilinum, to which it is perhaps even more similar morphologically.
Etymology: From the Latin peregrinus, foreign, having a tendency to wander. Referring to the ancestor of this species that must have wandered to these remote islands from South America.
by: M. Sundue, G. Rouhan and R.C. Moran
Description: Plants terrestrial; es erect, ca. 1.5 cm wide; fronds 0.35-1 m long; basal petiole scales 3.0 × 0.1-0.15 cm, linear-lanceolate, light brown, translucent, minutely denticulate, twisted, the cells elongate; laminae 30-60 cm long, 3-pinnate at base, 2-pinnate-pinnatifid medially; basal pinna 12-22 cm long, inaequilateral, short-stalked; pinnules sessile, the basal segments frequently overlapping the pinna rachis, the largest pinnule of the basal pinna 7-9 cm long; pinna rachises abaxially glandular, scaly, and densely pubescent, the glands sessile, globose, 0.1 mm long, the hairs 0.2-0.4 mm long, 3- or 4-celled, hyaline, acicular, the cross walls reddish, the scales 1.5-4.0 × 0.4-1.2 mm, ovate to lanceolate, translucent, light brown, slightly bicolorous, the center darker than the edges, entire, the cells isodiametric, adaxial pinna rachises not seen; costules abaxially glandular, scaly, and pubescent, the glands like those of the costae, the scales 1.5-2.5 × 0.5 mm, ovate to lanceolate, the apices attenuate, up to 1/3 the length of the scale, otherwise similar to those of the pinna rachises, the hairs similar to those of the abaxial costae, adaxial costules not seen; lamina tissue between the veins abaxially glandular and sparsely pubescent, the glands sessile, globose, 0.1 mm long, the hairs 0.2-0.3 mm long, 2-celled, erect, adaxially glandular and pubescent the glands sessile, globose, 0.1 mm long, the hairs 0.3-0.5 mm long, 3- or 4-celled, spreading; veins not visible on either side of the lamina, abaxially glandular, pubescent, and provided with scales along the main vein, the hairs 0.3-0.5 mm long, 3- or 4-celled, adaxially pubescent, the hairs like those between the veins; lamina margins recurved, ciliate, the hairs 0.2-0.4 mm long, 2- or 3-celled, acicular; indusia present, 0.3-0.4 mm wide, light brown, fugacious, the surface and margins with sessile glands, ca. 0.1 mm long, and sometimes with 1 or 2 setae, ca. 0.1 mm long; spores echinate (Tryon and Lugardon 1990: 460 as Ctenitis aquilina)
Distribution: Distribution and habitat.- Endemic to Gough Island in the South Atlantic Ocean, which is part of the Tristan da Cunha archipelago; among rocks, on banks, in the open, or under stands of Phylica arborea ca. 55-500 m.
Comments: Megalastrum peregrinum is distinguished from all other species in the circumaustral region by the lamina tissue between the veins adaxially pubescent and glandular. In other aspects, M. peregrinum is similar to M. spectabile of Chile and Argentina, M. aquilinum of Tristan da Cunha and Gough Islands, and M. taafense of Île Amsterdam and Île Saint-Paul. In addition to the indument of the adaxial laminae, it differs from M. spectabile in having recurved lamina margins, a fugacious indusia, and longer scales (1.5-2.5 mm long vs. 0.5-1.2 mm long) on the abaxial costules, and from M. aquilinum and. M. taafense by the adaxial indument, and having more densely ciliate lamina margins and longer scales (1.5-2.5 mm long vs. 1.0-1.5 mm long) on the abaxial costules. The South Altlantic islands of the Tristan archipelago, including Tristan da Cunha, the Nightingale group, Inaccessible, and Gough Island, are about 1750 miles west of South Africa and 2088 miles east of South America. Gough Island lies 230 miles southeast of the other islands in the Tristan da Cunha archipelago. All the islands are of recent volcanic origin, with ages of 1 million years (Tristan), 6 million years (Gough), 8 million years (Inaccessible), and 16 million years (Nightingale group) (Wace and Dickson 1965). The islands have a temperate flora that is low in diversity, but rich in ferns. About half of the vascular plant diversity is comprised of ferns and lycophytes (Christensen 1940; Tryon 1966; Wace and Holdgate 1958). The islands' flora is notable for its high endemism: at least half of its species or varieties of ferns and lycophytes are endemic (Christensen 1940; Tryon 1966). The addition of M. peregrinum brings the number of ferns and lycophyte species in the island group up to 34. Based on the young age of the Tristan da Cunha archipelago and the similarity of M. peregrinum to the South-American M. spectabile, an allopatric origin of this species through long-distance dispersal from South America is likely. A similar long-distance dispersal event has been inferred for several species in the "ciliatum group" of Elaphoglossum on Tristan da Cunha (Vasco et al. in press.). Alternatively, M. peregrinum might have evolved locally on the islands from M. aquilinum, to which it is perhaps even more similar morphologically.
Etymology: From the Latin peregrinus, foreign, having a tendency to wander. Referring to the ancestor of this species that must have wandered to these remote islands from South America.